Composition for forming anti-reflective coating for use in lithography

ABSTRACT

The present invention relates to a composition for forming anti-reflective coating for use in a lithography process in manufacture of a semiconductor device which comprises polymer (A) having a weight average molecular weight of 5,000 or less, and a polymer (B) having a weight average molecular weight of 20,000 or more. The composition provides an anti-reflective coating for use in a lithography which is excellent in step coverage on a substrate with an irregular surface, such as hole or trench, has a high anti-reflection effect, causes no intermixing with a resist layer, provides an excellent resist pattern, and has a higher dry etching rate compared with the resist layer.

TECHNICAL FIELD

The present invention relates to a novel composition for anti-reflectivecoating material, particularly to an anti-reflective coating for use inlithography that is excellent in coating performance on a substratehaving irregularity, such as holes or trenches, has a highanti-reflective effect, causes no intermixing with a resist layer togive an excellent resist pattern, and has a higher dry etching ratecompared with the resist, and more particularly to anti-reflectivecoating for use in dual damascene process for introducing Cu (copper) aswiring material used for reducing wiring delay in semiconductor devicesparticularly in recent years.

BACKGROUND ART

Conventionally, in the manufacture of semiconductor devices,micro-processing by lithography using a photoresist composition has beencarried out. The micro-processing is a processing method includingforming a thin film of a photoresist composition on a silicon wafer,irradiating actinic rays such as ultraviolet rays through a mask patterndepicting a pattern for a semiconductor device, developing it to obtaina resist pattern, and etching the silicon wafer using the resist patternas a protective film. However, in recent progress in high integration ofsemiconductor devices, there has been a tendency that shorter wavelengthactinic rays are being used, i.e., KrF excimer laser beam (248 nm) andfurther ArF excimer laser beam (193 nm) have been taking the place ofi-line (365 nm). Along with this change, influences of random reflectionand standing wave off a substrate have become serious problems.Accordingly, it has been widely studied to provide an anti-reflectivecoating between the photoresist and the substrate (BottomAnti-Reflective Coating, BARC).

As the anti-reflective coating, inorganic anti-reflective coatings madeof titanium, titanium dioxide, titanium nitride, chromium oxide, carbonor α-silicon and organic anti-reflective coatings made of alight-absorbing substance and a high molecular compound are known. Theformer requires an installation such as a vacuum deposition apparatus, aCVD (chemical vapor deposition) apparatus or a sputtering apparatus. Incontrast, the latter is considered advantageous in that it requires nospecial installation so that many studies have been made. For example,mention may be made of the acrylic resin type anti-reflective coatinghaving a hydroxyl group being a crosslinking reaction group and a lightabsorbing group in the same molecule as disclosed in U.S. Pat. No.5,919,599 and the novolak resin type anti-reflective coating having ahydroxyl group being a crosslinking reaction group and a light absorbinggroup in the same molecule as disclosed in U.S. Pat. No. 5,693,691, andso on.

The physical properties desired for organic anti-reflective coatingmaterials include high absorbance to light and radioactive rays, nointermixing with the resist layer (being insoluble in resist solvents),no diffusion of low molecular substances from the anti-reflectivecoating material into the topcoat resist upon coating or heat-drying,and a higher dry etching rate than the resist. They are described in,for example, Proc. SPIE, Vol. 3678, 174-185 and 800-809 (1999) and Proc.SPIE, Vol. 2195, 225-229 (1994).

Wiring delay has a more adverse effect on high-speed performance of LSIin LSI pattern rule having a fineness of 0.13 μm or less, and it becomesdifficult to proceed an improvement in performance of LSI due to thepresent status of LSI process technique. Materials used for reducingwiring delay are a wiring material Cu and an interlayer insulating filmhaving a low dielectric constant. And, a technique introduced forchanging from Al (aluminum) as a wiring material to Cu is dual damasceneprocess. The dual damascene process requires the use of ananti-reflective coating applied on a substrate having a larger aspectratio (irregularity) compared with a substrate produced by using theconventional wiring material Al.

For anti-reflective coatings for dual damascene process, it is requiredto control a shape of an anti-reflective coating applied at theperiphery of holes on a primary substrate. There are known the followingtwo methods and anti-reflective coatings for controlling a shape of ananti-reflective coating applied at the periphery of holes on a primarysubstrate.

One of them is a method of full-fill type in which an anti-reflectivecoating is used in such a manner that holes are fully filled with theanti-reflective coating to make the surface of a substrate planarized.In this method, it is desirable to fill approximately 100% of holes withthe anti-reflective coating. The merit of this method is advantages inlithographic process, while the demerit is disadvantages in etchingprocess.

Another is a method of partial-fill type in which an anti-reflectivecoating is used in such a manner that holes are partially filled withthe anti-reflective coating to cover the bottom parts and edge upperparts of the holes.

In this method, it is desirable that the filling rate of holes is around20 to 80%. The merit of this method is advantages in semiconductorproduction that as the filling rate of holes is 20 to 80%, etchingprocess for removing the anti-reflective coating can be carried out fora shorter time compared with a case where the filling rate of holes isapproximately 100%. However, the demerit is disadvantages in lithographyprocess in terms of an anti-reflective effect as a substrate havingholes is not completely planarized. In addition, this method isgenerally used for substrates with a low integrated degree of a wiringwidth of 0.3 μm or more, because the method of partial-fill type oftenrequires simultaneous use of another anti-reflective coating in order touse in a part of the substrate with a high integrated degree of a wiringwidth of 0.2 μm or less, unlike in the case where the anti-reflectivecoating in full-fill type is used in a part of the substrate with a highintegrated degree of a wiring width of 0.2 μm or less.

As demand characteristics for the material for forming anti-reflectivecoating used in the partial-fill type, it is important to have thefollowing performances when the anti-reflective coating is applied at aconstant thickness:

-   (1) the filling amount of anti-reflective coating in holes is 20 to    80%, preferably 30 to 70% based on the volume of holes;-   (2) the anti-reflective coating filled in holes has no void or gap;-   (3) no anti-reflective coating is adhered to the side wall of holes;-   (4) the edge upper part of the holes is covered with anti-reflective    coating;-   (5) anti-reflective coating has a constant thickness regardless of    the density of holes on a substrate; and-   (6) no resist poising occurs.    The anti-reflective coating fully satisfying these six performances    is needed.

In particular, materials for forming anti-reflective coating require thefollowings when an anti-reflective coating is applied at a constantthickness

-   -   the filling rate of holes with anti-reflective coating is 20 to        80%, preferably 30 to 70% based on the volume of holes;    -   no void or gap is present in holes; and    -   the anti-reflective coating has a constant thickness regardless        of the density of holes on a substrate.

As an example in which the conventional material for forminganti-reflective coating used in the partial-fill type is used, forexample Japanese Patent Laid-open No. 2000-294504 discloses a method forforming photoresist relief image over a substrate having topography inwhich (a) a layer of anti-reflective composition containing a polymerhaving a molecular weight of about 8,000 or less is applied on thesubstrate; (b) a photoresist layer is applied on the layer ofanti-reflective composition; and (c) the photoresist layer is exposed toan activated radiation, and the exposed photoresist layer is developed.The publication describes a preferable embodiment in which ananti-reflective composition exhibits a degree of planarization of about0.5 or more for a step having slope shape formed by a local oxidation ofsilicon and a width of 0.8 μm and a depth at middle point of 2 μm.However, the publication does not describe the formation of void or gapof air that has a tendency to exert an adverse effect when theanti-reflective coating is applied and that is an important point in acase where the material for forming anti-reflective coating is used inpartial-fill type, and nor describe whether or not the thickness of theanti-reflective coating is constant regardless of the density of holeson a substrate.

An object of the present invention is to provide a composition forforming anti-reflective coating for use in lithography which has afilling rate of holes with anti-reflective coating of 20 to 80% and novoid or gap of air in the holes when the anti-reflective coating isapplied at a constant thickness; gives an anti-reflective coating havinga constant thickness regardless of the density of holes on thesubstrate; has a high prevention effect of reflected light; causes nointermixing with a resist layer; provide an excellent resist pattern;and has a higher dry etching rate compared with the resist, and toprovide a method for forming resist pattern by using the composition forforming anti-reflective coating.

That is, polymers and compositions for forming anti-reflective coatingdisclosed in the present application are more appropriate for theanti-reflective coating of partial-fill type that is used to obtainanti-reflective performance and a high dry etching rate for applying tosemiconductor devices having a relatively wide wiring width, rather thanfor the anti-reflective coating of full-fill type that is used to obtainanti-reflective performance by fully filling holes on a substrate andplanarizing it for applying to semiconductor devices having a relativelynarrow wiring width.

DISCLOSURE OF INVENTION

The present invention relates to the following aspects:

-   -   as a first aspect, a composition for forming anti-reflective        coating, comprising a polymer (A) having a weight average        molecular weight of 5,000 or less, and a polymer (B) having a        weight average molecular weight of 20,000 or more;    -   as a second aspect, the composition for forming anti-reflective        coating as described in the first aspect, wherein the        polymer (A) is a halogenated bisphenol A resin having a weight        average molecular weight of 700 to 5,000;    -   as a third aspect, the composition for forming anti-reflective        coating as described in the second aspect, wherein the        halogenated bisphenol A resin comprises at least a polymer of        formula (1):        wherein X¹ is a halogen atom, n1 is the number of repeated units        and an integer of 1 to 50, n2 and n3 is the number of        substituent X¹ on a benzene ring and an integer of 1 to 3, and Y        is a group of formula (2)        wherein T¹ is a divalent linking group, P is a (n4+1) valent        aromatic ring group having 6 to 14 carbon atoms, M is an        electron-donating group, n4 is the number of substituent M on P        and an integer of 0 to 3, in a case where n4 is 2 or 3,        substituents M are the same or different from each other;    -   as a fourth aspect, the composition for forming anti-reflective        coating as described in the first aspect, wherein the        polymer (A) is a halogen-containing novolak resin having a        weight average molecular weight of 600 to 5,000;    -   as a fifth aspect, the composition for forming anti-reflective        coating as described in the fourth aspect, wherein the        halogen-containing novolak resin is a polymer having at least a        repeated unit of formula (3):        wherein T² is a divalent linking group, X² is chlorine atom or        bromine atom, n5 is the number of repeated units, n6 is the        number of substituent X² on a benzene ring and an integer of 1        to 3, P is a (n7+1) valent aromatic ring group having 6 to 14        carbon atoms, M is an electron-donating group, n7 is an integer        of 0 to 3, in a case where n7 is 2 or 3, a plurality of M are        the same or different from each other;    -   as a sixth aspect, the composition for forming anti-reflective        coating as described in any one of the first to fifth aspects,        wherein the polymer (B) is a polyacrylate or polymethacrylate        having a weight average molecular weight of 20,000 to 200,000;    -   as a seventh aspect, the composition for forming anti-reflective        coating as described in any one of the first to fifth aspects,        wherein the polymer (B) is a polystyrene or a derivative thereof        having a weight average molecular weight of 20,000 to 200,000;    -   as an eighth aspect, the composition for forming anti-reflective        coating as described in any one of the first to seventh aspects,        containing the polymer (A) in an amount of 33.7 to 83.2% by        weight and the polymer (B) in an amount of 66.3 to 16.8% by        weight;    -   as a ninth aspect, the composition for forming anti-reflective        coating as described in any one of the first to eighth aspects,        further containing a crosslinking agent having at least two        crosslink-forming functional groups;    -   as a tenth aspect, the composition for forming anti-reflective        coating as described in any one of the first to ninth aspects,        wherein the composition is used for a production of a        semiconductor device by a method comprising covering a substrate        having holes of an aspect ratio indicated by height/diameter of        1 or more with a photoresist, and transferring an image on the        substrate by utilizing lithography process, and the composition        is used for partially filling the holes on the substrate prior        to a covering with the photoresist;    -   as an eleventh aspect, the composition for forming        anti-reflective coating as described in the tenth aspect,        wherein the filling of the holes is carried out in a rate of 20        to 80% based on a volume per hole; and    -   as a twelfth aspect, a process for manufacturing a semiconductor        device by transferring an image on a substrate and forming an        integrated circuit element, comprising the steps (I), (II)        and (III) of:        -   Step (I): a step comprising coating the composition for            forming anti-reflective coating as described in any one of            the first to ninth aspects on a substrate having an aspect            ratio indicated by height/diameter of 1 or more, and drying            the composition to fill 20 to 80% of a volume of holes on            the substrate with the anti-reflective coating;        -   Step (II): a step comprising coating a resist and drying it;            and        -   Step (III): a step comprising exposing to light, developing            and etching.

The present invention relates to a composition for forminganti-reflective coating for use in a lithographic process in manufactureof a semiconductor device, comprising a polymer (A) having a weightaverage molecular weight of 5,000 or less, and a polymer (B) having aweight average molecular weight of 20,000 or more. As the polymers,polymers having halogen atoms in the main chain thereof can bepreferably used.

Although the polymer (A) having a weight average molecular weight of5,000 or less for forming the anti-reflective coating of the presentinvention may vary depending on the coating solvents used, the viscosityof the solution, the shape of the coating, etc., a novolak resin, abisphenol A resin, a polyester resin or a polyether resin, etc. can bepreferably used.

Although the polymer (B) having a weight average molecular weight of20,000 or more for forming the anti-reflective coating of the presentinvention may vary depending on the coating solvents used, the viscosityof the solution, the shape of the coating, etc., an acrylic resin, apolyester resin, a polyvinyl phenol resin or a polyimide resin, etc. canbe preferably used.

In particularly, it is preferable that the above-mentioned polymerscomprise a halogen-containing novolak resin and/or the derivativethereof, and an acrylic resin and/or the derivative thereof.

The weight ratio of polymers in the resulting anti-reflective coating is33.7 to 83.2% by weight of the polymer (A) having a weight averagemolecular weight of 5,000 or less and 16.8 to 66.3% by weight of thepolymer (B) having a weight average molecular weight of 20,000 or more,preferably 50.0 to 75.0% by weight of the polymer (A) having a weightaverage molecular weight of 5,000 or less and 25.0 to 50.0% by weight ofthe polymer (B) having a weight average molecular weight of 20,000 ormore.

The composition for forming anti-reflective coating according to thepresent invention contains the above-mentioned polymers and a solvent,and may further contain a crosslinking agent, other additives, etc. Asolid content in the composition for forming anti-reflective coatingaccording to the present invention is 0.1 to 50% by weight. In addition,the content of the above-mentioned polymers is 0.1 to 50 parts byweight, preferably 1 to 30 parts by weight based on 100 parts by weightof the whole composition.

The polymers in the present invention may be any of random copolymers,block copolymers and graft copolymers. The polymers for forming theanti-reflective coating of the present invention can be synthesized byvarious methods such as radical polymerization, anionic polymerizationor cationic polymerization. As the type of polymerization, variousmethods such as solution polymerization, suspension polymerization,emulsion polymerization or bulk polymerization are possible.

As the polymer (A), for example halogenated bisphenol A resins having aweight average molecular weight of 700 to 5,000 can be used.

The halogenated bisphenol A resins are preferably polymers of at leastformula (1).

The halogenated bisphenol A resins can be synthesized by apolycondensation of a halogenated bisphenol A with epichlorohydrin. Thehalogenated bisphenol A includes for example tetrabromobisphenol A ortetrachlorobisphenol A, and as goods on the market, halogenatedbisphenol A resins having a halogen content of 46 to 52% and an epoxyequivalent of 330 to 700 g/eq are easily available.

The halogenated bisphenol A resins have epoxy groups at the terminals,at least one of the epoxy groups may be reacted with a compound thatreacts with the epoxy group.

The terminal structure of the halogenated bisphenol A resins ispreferably the structure of formula (2) having a light-absorbing moiety.

In formula (1), X¹ is a halogen atom, such as bromine atom, chlorineatom, etc., n1 is the number of repeated units, and is 1 to 50,preferably 1 to 10, n2 and n3 are the number of substituents substitutedby halogen atoms on the benzene ring, and are 1 to 3, preferably 2.

In formula (2), P is a (n4+1) valent aromatic ring group having 6 to 14carbon atoms, for example a light absorbing group, such as benzene ring,naphthalene ring, anthracene ring, etc.

M is an electron-donating group. M includes for example substituents,such as —OH, —OR², —R², —N(R³)(R⁴) or —SR⁴, R² is a hydrocarbon grouphaving carbon atom of 1 to 20, R³ and R⁴ may be the same or differentfrom each other, and are hydrogen atom or a hydrocarbon group havingcarbon atom of 1 to 20. The above-mentioned M includes for examplemethyl, ethyl, butyl, hydroxy, methoxy, ethoxy, allyl, vinyl, amino,etc. n4 is the number of substituent M on P, and is an integer of 0 to3. In a case where n4 is 2 to 3, M may be the same or different fromeach other.

It is necessary that at least one epoxy group at both terminals of thehalogenated bisphenol A resin has the structure which Y in formula (1)is the group of formula (2) by reaction with an aromatic compound, suchas an aromatic organic acid, an aromatic amine, aromatic alcohol, etc.As these aromatic compounds, there can be used compounds substitutedwith one or two functional groups, such as carboxyl group, sulfonicgroup, amino group, hydroxy group, etc. on an aromatic ring, such asbenzene ring, naphthalene ring, anthracene ring, etc. These are aromaticcompounds having an absorption at an ultraviolet portion, for examplebenzoic acid, benzenesulfonic acid, aniline, benzyl amine, phenol,naphthalenecarboxylic acid, naphthyl acetic acid, naphthalenesulfonicacid, naphthyl amine, naphthol, anthracenecarboxylic acid,anthracenesulfonic acid, aminoanthracene, hydroxyanthracene andderivatives thereof. When the structure which the portion of Y is thegroup of formula (2) is formed by reacting these aromatic compounds witha halogenated bisphenol A resin, divalent linking group (T¹) has astructure, such as —O—CO—, —SO₂—O—, —NH—, —O—, etc.

Among the aromatic compounds, 9-anthracenecarboxylic acid isparticularly preferable. In a case where 9-anthracenecarboxylic acid isused, (T¹) in formula (2) is —O—CO— and (P) is anthryl.

The other epoxy group at both terminals of the halogenated bisphenol Aresin can react with an aliphatic organic acid, an aliphatic alcohol, analiphatic amine or water. The reaction leads to the structure of formula(4)

wherein Y is a group of formula (6)

In formula (6), Z is a substituent, such as RCOO—, RO—, RNH—, HO—, etc.in which R is a group of a hydrocarbon that may be substituted.

Depending on the reaction condition, the other epoxy group at bothterminals of the halogenated bisphenol A resin may be in an unreactedstate. In this case, Y in formula (4) has a structure of formula (5)

Therefore, the halogenated bisphenol A resin used in the presentinvention has structures of formulae (2), (5) and (6) at both terminalsY in formula (4). As to these terminals Y, the proportion of formula(2): formula (5): formula (6) is 0.5-1.0:0-0.5:0-0.5, preferably0.8-1.0:0-0.2:0-0.2 in molar number of each repeated unit in a casewhere the total molar number of formulae (2), (5) and (6) is set to 1.

The halogenated bisphenol A resin used in the present invention ispreferably a resin having a structure of formula (7)

obtained by reacting epoxy groups at both terminals with9-anthracenecarboxylic acid.

In addition, also resins having a structure of formula (8)

can be used.

The hydroxy groups in the structure of the above-mentioned halogenatedbisphenol A resin can be reacted with a crosslink-forming functionalgroup in a crosslinking agent to form a crosslinking structure in theresulting anti-reflective coating.

It is essential that at least one Y has a structure of formula (2) byreacting an epoxy group at a terminal of the halogenated bisphenol Aresin with an aromatic compound having a light absorption. There arecases where Ys at both terminals have the structure of formula (2),where one Y has the structure of formula (2) and the other Y has thestructure of formula (5), and where one Y has the structure of formula(2) and the other Y has the structure of formula (6).

As halogen atoms having a large atomic weight, particularly bromineatoms are contained in the composition of the present invention, ananti-reflective coating formed from the composition has a high dryetching rate. In order to improve a rate of light absorbing groups perunit weight of a composition for forming anti-reflective coating, it ispreferable that a rate of formula (2) is higher in the portion of Y inthe halogenated bisphenol A resin.

The halogenated bisphenol A resin is produced by polymerization of ahalogenated bisphenol A, such as tetrabromobisphenol A withchloromethyloxirane, such as epichlorohydrin.

For example, the polymer (A) may be a halogen-containing novolak resinhaving a weight average molecular weight of 700 to 5,000.

The halogen-containing novolak resin is a polymer having at least arepeated unit of formula (3).

The halogen-containing novolak resin may further contain, in addition toa repeated unit of formula (3), repeated units of formulae (9) and (10)

wherein X² is chlorine atom or bromine atom, n6 is the number ofsubstituent X² on a benzene ring and an integer of 1 to 3, Z is asubstituent, such as RCOO—, RO—, RNH—, HO—, etc., n8, n9 and n5 aremolar numbers of each repeated units in a case where total molar numberof repeated units of formulae (3), (9) and (10) is set to 1, the sum ofn8, n9 and n9 is 1, n8 is 0 to 0.8, n9 is 0 to 0.8 and n5 is 0.2 to 1.0.

The halogen-containing novolak resin can be easily produced by preparinga halogen-containing novolak resin having an epoxy group of formula (9),and carrying out an addition reaction of it with a compound that reactswith the epoxy group to convert into a compound having repeated units offormulae (3) and (10). In this process, a resin having repeated units offormulae (3) and (10) is produced by using at least one compound thatreacts with the epoxy group.

The repeated unit of formula (3) is a moiety to which a light absorbingmaterial is bound, and is obtained by subjecting the resin of formula(9) to an addition reaction with a light absorbing material. The lightabsorbing material is a compound substituted with one or more functionalgroups, such as carboxyl group, sulfonic group, amino group, hydroxygroup, etc on benzene ring, naphthalene ring, anthracene ring or pyrenering. These compounds may be further substituted with —OR², —N(R³)(R⁴)or —SR⁴ wherein R² is a group of a hydrocarbon having carbon atom of 1to 20, and R³ and R⁴ are the same or different from each other, hydrogenatom or a group of hydrocarbon of carbon atom of 1 to 20.

After these light absorbing materials are reacted with the epoxy groupin formula (9), a divalent linking group (T²) has a structure of —O—CO—,—SO₂—O—, —NH—, —O—, etc.

These light absorbing materials have carboxyl group or a functionalgroup that can be converted into carboxyl group, and preferably reactswith an epoxy group in formula (9) to be bonded thereto. The carboxylgroup or functional group that can be converted into carboxyl group isadded to the epoxy group in the resin of formula (9) to form the resinhaving the repeated unit of formula (3). Particularly preferable lightabsorbing material is 9-anthracenecarboxylic acid, and affords a resinof formula (11)

wherein n10, n11 and n12 are molar numbers of each repeated units in acase where total molar number of repeated units constituting the resinis set to 1, the sum of n10, n11 and n12 is 1, n10 is 0 to 0.8, n11 is 0to 0.8 and n12 is 0.2 to 1.0, n6 is the number of bromine atomssubstituted on the benzene ring and an integer of 1 to 3.

In a case where 9-anthracenecarboxylic acid is used, (T²) in formula (3)is —O—CO— and (P) is anthryl.

A light absorbing material having carboxyl group or a functional groupthat can be converted into carboxyl group is bound to a resin having therepeated unit of formula (9) by addition reaction to give a resin havingthe repeated unit of formula (3). In this case, epoxy groups remainingon the resin having the repeated unit of formula (9) can be subjected tohydrolysis to form the repeated unit of formula (10) (Z=—OH) to which ahydroxy group is added.

In addition, the repeated units of formulae (3) and (10) are alsomoieties to which a crosslinking reactive group (a hydroxy group) isbound.

The repeated units of formulae (3) and (10) are structural unitsaffording light absorption and regulate the rate of crosslinkingreaction with a crosslinking agent. That is, the crosslinking reactionrate is regulated by varying molar number of each repeated unit offormulae (3) and (10) in a case where the total molar number of formulae(3) and (10) is set to 1.

In formulae (3), (9) and (10), the molar ratio of n8: n9: n5 is0-0.8:0-0.8: 0.2-1, preferably 0-0.2:0-0.2:0.8-1, more preferably0-0.1:0-0.1:0.9-1 in molar number of each repeated unit in a case wherethe total molar number of formulae (3), (9) and (10) is set to 1, andn8+n9+n5 equals 1.

Also in formula (11), the molar ratio of n10: n11: n12 is0-0.8:0-0.8:0.2-1, preferably 0-0.2:0-0.2:0.8-1, more preferably0-0.1:0-0.1:0.9-1 in molar number of each repeated unit in a case wherethe total molar number of repeated units constituting the resin is setto 1, and n10+n11+n12 equals 1.

The repeated unit of formula (3) is essential for bonding a lightabsorbing material to the halogen-containing novolak resin having theepoxy group of formula (9) by addition reaction. When the lightabsorbing materials are bound to all epoxy groups by addition reaction,the number of the repeated unit of formula (9) is zero. The structuralunit consisted of formulae (3), (9) and (10) is represented by theproportion of each repeated unit in a case where the total molar numberof formulae (3), (9) and (10) is set to 1, that is, in a case where thetotal molar number of the repeated unit in each monomer constituting theresulting resin is set to 1,

As the present invention uses resins containing halogen atoms having alarge atomic weight, particularly bromine atoms, many repeated units offormula (3) are required to be contained in the structure in order toimprove the proportion of light absorbing groups per unit weight ofanti-reflective coating material when an anti-reflective coatingmaterial containing the resins is applied.

It can be preferably used the resin of formula (12) produced by bondingonly light absorbing materials to all or a part of epoxy groups in theresin of formula (9) and converting into the repeated unit of formula(3).

wherein X² is chlorine atom or bromine atom, n6 is the number ofsubstituent X² on a benzene ring and an integer of 1 to 3, P is a (n7+1)valent aromatic ring group having 6 to 14 carbon atoms, M is anelectron-donating group, n7 is an integer of 0 to 3, in a case where n7is 2 or 3, a plurality of M are the same or different from each other,n13 and n14 are molar numbers of each repeated units in a case wheretotal molar number of repeated units of monomers constituting the resinis set to 1, the sum of n13 and n14 is 1, n13 is 0 to 0.8 and n14 is 0.2to 1.0.

In the resin of formula (12), the resins of formula (13) produced undera condition causing no hydrolysis can be preferably used.

In the meantime, n8, n9 and n5 are the proportion of each repeated unitof formulae (9), (10) and (3) in the resulting resin, and there may bepresent not only in the structure composed of—repeated unit of formula(9)—repeated unit of formula (10)—repeated unit of formula (3)—but alsoin the structure composed of arbitrary combinations, such as thestructure composed of—repeated unit of formula (9)—repeated unit offormula (3)—repeated unit of formula (10)—, —repeated unit of formula(9)—repeated unit of formula (3)—repeated unit of formula (3)—repeatedunit of formula (10)—, —repeated unit of formula (9)—repeated unit offormula (3)—or —repeated unit of formula (9)—repeated unit of formula(3)—repeated unit of formula (3)—. The resins may be in any structuresso long as the molar portion of n8: n9: n5 is 0-0.8:0-0.8:0.2-1.

The resin of formula (3) is synthesized by reacting a resin of formula(9) with a light absorbing material in a solvent, such as propyleneglycol monomethyl ether or propylene glycol monomethyl ether acetate inthe presence of a catalyst, such as benzyltriethylammonium chloride ortetramethylammonium hydroxide at a temperature of 100 to 130° C. under anormal pressure for 12 to 48 hours.

The polymer (B) used in the present invention has a weight averagemolecular weight of 20,000 or more. A light absorbing materialcorresponding to the above-mentioned P may be bound to the polymer (B).For example, a light absorbing material corresponding to theabove-mentioned P can be bound to a structural unit having a glycidylgroup by addition reaction to obtain a polymer (B) having a lightabsorbing moiety. However, the polymer (B) does not necessarily requireto possess a light absorbing moiety.

The polymer (B) needs to have a crosslink-forming functional group, suchas hydroxy group, and can be obtained by polymerizing monomers havinghydroxy group or monomers having a functional group that causes hydroxygroup by a reaction.

As the polymer (B), for example acrylic ester or methacrylic esterhaving a weight average molecular weight of 20,000 to 200,000 can beused.

Poly(meth)acrylates as the polymer (B) that can be used are for examplepoly(meth)acrylate having a hydroxy group or poly(meth)acrylate havingan epoxy group.

These compounds can be produced by polymerizing solely hydroxymethylmethacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate,hydroxybutyl methacrylate, hydroxypentyl methacrylate, hydroxyphenylmethacrylate, hydroxypropyl acrylate, glycidyl acrylate, glycidylmethacrylate or the like, or by copolymerizing two or more of thesemonomers.

The polymer (B) used in the present invention includes for examplepolystyrene or a derivative thereof having a weight average molecularweight of 20,000 to 200,000. These resins may be polyhydroxystyreneshaving a functional group, such as hydroxy group which can form acrosslink with a crosslinking agent.

It is possible to copolymerize monomers other than the above-describedmonomers into the polymer (B). This allows minute adjustment ofcrosslinking reaction rate, dry etching rate, reflectivity, etc. Such acopolymerizable monomer includes, for example, compounds having at leastone addition polymerizable unsaturated bond selected from acrylic acid,methacrylic acid, maleic acid, fumaric acid, acrylic acid esters,acrylamides, methacrylic acid esters, methacrylamides, allyl compounds,vinyl ethers, vinyl esters, styrenes, crotonic acid esters, etc.

The acrylic acid esters include, for example, alkyl acrylates having 1to 10 carbon atoms in the alkyl group.

The methacrylic acid esters include, for example, alkyl methacrylateshaving 1 to 10 carbon atoms in the alkyl group.

The acrylamides include, for example, acrylamide, N-alkylacrylamides,N-arylacrylamides, N,N-dialkylacrylamides, N,N-diarylacrylamides,N-methyl-N-phenylacrylamide, N-2-acetamide ethyl-N-acetylacrylamide,etc.

The methacrylamides include, for example, methacrylamide,N-alkylmethacrylamides, N-arylmethacrylamides,N,N-dialkylmethacrylamides, N,N-diarylmethacrylamides,N-methyl-N-phenylmethacrylamide, N-ethyl-N-phenylmethacrylamide, etc.

The vinyl ethers include, for example, alkyl vinyl ethers, vinyl arylethers, etc.

The vinyl esters include, for example, vinyl butyrate, vinylisobutyrate, vinyl trimethylacetate, etc.

The styrenes include, for example, styrene, alkylstyrenes,alkoxystyrenes, halogenated styrenes, carboxystyrenes, etc.

The crotonic acid esters include, for example, alkyl crotonates such asbutyl crotonate, hexyl crotonate, glycerin monocrotonate, etc.

Also, mention may be made of dialkyl itaconates, monoalkyl esters ordialkyl esters of maleic acid or fumaric acid, maleimide, acrylonitrile,methacrylonitrile, maleylonitrile, etc. In addition, generally, additionpolymerizable unsaturated compounds may be used.

The anti-reflective coating forming composition of the present inventionmay further contain a crosslinking agent having at least twocrosslink-forming functional groups. The crosslinking agent includes,for example, melamines, substituted ureas, polymers having epoxy groupsand the like. The agent is preferably methoxymethylated glycoluril,methoxymethylated melamine or the like, more preferablytetramethoxymethyl glycoluril or hexamethoxymethyl melamine. Theaddition amount of the crosslinking agent may vary depending on thecoating solvents used, the underlying substrate used, the viscosity ofthe solution required, the shape of the coating required, etc., andusually 0.001 to 20 parts by weight, preferably 0.01 to 10 parts byweight, more preferably 0.1 to 5.0 parts by weight based on 100 parts byweight of the total composition.

As catalyst for promoting the above-mentioned crosslinking reaction inthe anti-reflective coating forming composition of the presentinvention, acid compounds, such as p-toluenesulfonic acid,trifluoromethanesulfonic acid, pyridinium p-toluenesulfonate, salicylicacid, sulfosalicylic acid, citric acid, benzoic acid, hydroxybenzoicacid, etc. or/and thermal acid generators, such as2,4,4,6-tetrabromocyclohexadienone, benzointosylate,2-nitrobenzyltosylate, etc. may be added. The blending amount thereof is0.02 to 10 parts by weight, preferably 0.04 to 5 part by weight based on100 parts by weight of the total solid content.

The anti-reflective coating forming composition of the present inventionmay contain further light absorbing agents, rheology controlling agents,adhesion auxiliaries, surfactants, etc. in addition to the abovedescribed ones, if necessary.

As the further light absorbing agents, the followings can be suitablyused: for example commercially available light absorbing agentsdescribed in “Technique and Market of Industrial Pigments” (CMCPublishing Co., Ltd.) or “Dye Handbook” (edited by The Society ofSynthetic Organic Chemistry, Japan), such as C. I. Disperse Yellow 1, 3,4, 5, 7, 8, 13, 23, 31, 49, 50, 51, 54, 60, 64, 66, 68, 79, 82, 88, 90,93, 102, 114 and 124; C. I. Disperse Orange 1, 5, 13, 25, 29, 30, 31,44, 57, 72 and 73; C. I. Disperse Red 1, 5, 7, 13, 17, 19, 43, 50, 54,58, 65, 72, 73, 88, 117, 137, 143, 199 and 210; C. I. Disperse Violet43; C. I. Disperse Blue 96; C. I. Fluorescent Brightening Agent 112, 135and 163; C. I. Solvent Orange 2 and 45; C. I. Solvent Red 1, 3, 8, 23,24, 25, 27 and 49; C. I. Pigment Green 10; C. I. Pigment Brown 2, andthe others. The light absorbing agent is usually blended in an amount of10 parts by weight or less, preferably 5 parts by weight or less basedon 100 parts by weight of the total composition.

The rheology controlling agents are added mainly aiming at increasingthe flowability of the anti-reflective coating forming composition andin particular in the baking step, increasing filling property of theanti-reflective coating forming composition into the inside of holes.Specific examples thereof include phthalic acid derivatives such asdimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dihexylphthalate or butyl isodecyl phthalate; adipic acid derivatives such asdi-n-butyl adipate, diisobutyl adipate, diisooctyl adipate or octyldecyladipate; maleic acid derivatives such as di-n-butyl maleate, diethylmaleate or dinonyl maleate; oleic acid derivatives such as methyloleate, butyl oleate or tetrahydrofurfuryl oleate; or stearic acidderivatives such as n-butyl stearate or glyceryl stearate. The rheologycontrolling agents are blended in proportions of usually less than 30parts by weight based on 100 parts by weight of the total composition.

The adhesion auxiliaries are added mainly for the purpose of increasingthe adhesion between the substrate or resist and the anti-reflectivecoating forming composition, in particular preventing the detachment ofthe resist in development. Specific examples thereof includechlorosilanes such as trimethylchlorosilane, dimethylvinylchlorosilane,methyldiphenylchlorosilane or chloromethyldimethyl-chlorosilane;alkoxysilanes such as trimethylmethoxysilane, dimethyldiethoxysilane,methyldimethoxysilane, dimethylvinylethoxysilane,diphenyldimethoxysilane or phenyltriethoxysilane; silazanes such ashexamethyldisilazane, N,N′-bis(trimethylsilyl)urea,dimethyltrimethylsilylamine or trimethylsilylimidazole; silanes such asvinyltrichlorosilane, γ-chloropropyltrimethoxysilane,γ-aminopropyltriethoxy-silane or γ-glycidoxypropyltrimethoxysilane;heterocyclic compounds such as benzotriazole, benzimidazole, indazole,imidazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole,2-mercaptobenzoxazole, urazole, thiouracyl, mercaptoimidazole ormercaptopyrimidine; ureas such as 1,1-dimethylurea or 1,3-dimethylurea,or thiourea compounds. The adhesion auxiliaries are added in proportionsof usually less than 5 parts by weight, preferably less than 2 parts byweight, based on 100 parts by weight of the total composition of theanti-reflective coating for lithography.

The anti-reflective coating forming composition of the present inventionmay contain surfactants with view to preventing the occurrence ofpinholes or striations and further increasing coatability not to causesurface unevenness. As the surfactants, mention may be made of, forexample, nonionic surfactants such as polyoxyethylene alkyl ethers,e.g., polyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, etc.,polyoxyethylene alkyl allyl ethers, e.g., polyoxyethylene octyl phenolether, polyoxyethylene nonyl phenol ether;polyoxyethylene/polyoxypropylene block copolymers, sorbitan fatty acidesters, e.g., sorbitan monolaurate, sorbitan monopalmitate, sorbitanmonostearate, sorbitan monooleate, sorbitan trioleate, sorbitantristearate, etc., polyoxyethylene sorbitan fatty acid esters, e.g.,polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan trioleate, polyoxyethylene sorbitan tristearate, etc.; fluorinebased surfactants, e.g., EFTOP EF301, EF303, EF352 (Tochem Products Co.,Ltd.), MEGAFAC R08, R30, LS-14 (Dainippon Ink and Chemicals, Inc.),FLUORAD FC430, FC431 (Sumitomo 3M Limited), ASAHI GUARD AG710, SURFLONS-382, SC101, SC102, SC103, SC104, SC105, SC106 (Asahi Glass Co., Ltd.),organosiloxane polymer KP341 (Shinetsu Chemical Co., Ltd.), etc. Theblending amount of the surfactants is usually 1 part by weight or less,preferably 0.5 part by weight or less, based on 100 parts by weight ofthe total composition of the present invention. The surfactants may beadded singly or two or more of them may be added in combination.

In the present invention, as the solvents for dissolving theabove-described resin, use may be made of ethylene glycol monomethylether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethylcellosolve acetate, diethylene glycol monomethyl ether, diethyleneglycol monoethyl ether, propylene glycol, propylene glycol monomethylether, propylene glycol monomethyl ether acetate, propylene glycolpropyl ether acetate, toluene, xylene, methyl ethyl ketone,cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, ethyl2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate,methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl3-methoxypropionate, ethyl 3-ethoxypropionate, methyl3-ethoxypropionate, methylpyruvate, ethyl pyruvate, ethyl acetate, butylacetate, ethyl lactate, butyl lactate, etc. The organic solvents may beused singly or in combination of two or more of them.

Further, high boiling solvents such as propylene glycol monobutyl etheror propylene glycol monobutyl ether acetate may be mixed. Among thesolvents, propylene glycol monomethyl ether, propylene glycol monomethylether acetate, ethyl lactate, butyl lactate, and cyclohexanone arepreferred for increasing the leveling property.

As resists to be coated as an upper layer of the anti-reflective coatingformed by using the composition of the present invention, any ofnegative type and positive type resists may be used and such a resistincludes a positive type resist consisting of a novolak resin and1,2-naphthoquinone diazide sulfonic acid ester, a chemically-amplifiedtype resist which consists of a photoacid generator and a binder havinga group which is decomposed with an acid and increases alkalidissolution rate, a chemically-amplified type resist consisting of analkali-soluble binder, a photoacid generator, and a low molecularcompound which is decomposed with an acid and increases the alkalidissolution rate of the resist, a chemically-amplified resist consistingof a photoacid generator, a binder having a group which is decomposedwith an acid and increases the alkali dissolution rate, and a lowmolecular compound which is decomposed with an acid and increases thealkali dissolution rate of the resist, for example a resist of tradename APEX-E manufactured by Shipley Co., Inc.

As the developer for the above-mentioned positive type photoresisthaving the anti-reflective coating for lithography formed by using theanti-reflective coating forming composition of the present invention,use may be made of aqueous solutions of alkalis, e.g., inorganic alkalissuch as sodium hydroxide, potassium hydroxide, sodium carbonate, sodiumsilicate, sodium metasilicate or aqueous ammonia, primary amines such asethylamine or n-propylamine, secondary amines such as diethylamine ordi-n-butylamine, tertiary amines such as triethylamine ormethyldiethylamine, alcohol amines such as dimethylethanolamine ortriethanolamine, quaternary ammonium salts such as tetramethylammoniumhydroxide, tetraethylammonium hydroxide or choline, cyclic amines suchas pyrrole or piperidine, etc. Furthermore, a suitable amount ofalcohols such as isopropyl alcohol or surfactants such as nonionicsurfactant can be added to the aqueous solution of above-describedalkalis. Among these, a preferred developer includes quaternary ammoniumsalts, more preferably tetramethylammonium hydroxide and choline.

The process for manufacturing a semiconductor device by using theanti-reflective material of the present invention and by transferring animage on a substrate and forming an integrated circuit element,comprising the steps (I), (II) and (III) of:

-   -   Step (I): a step comprising coating the composition for forming        anti-reflective coating on a substrate having holes of an aspect        ratio indicated by height/diameter of 1 or more, and drying the        composition to fill 20 to 80%, preferably 30 to 70% of a volume        of holes on the substrate with the anti-reflective coating;    -   Step (II): a step comprising coating a resist and drying it; and    -   Step (III): a step comprising exposing to light, developing and        etching.        The conditions of baking after the anti-reflective coating        composition is coated are 80 to 250° C. for 1 to 120 minutes.

As mentioned above, the material for forming anti-reflective coatingaccording to the present invention is used for a production of asemiconductor device by a method comprising covering a substrate havingholes of an aspect ratio indicated by height/diameter of 1 or more,generally 1 to 50 with a photoresist, and transferring an image on thesubstrate by utilizing lithography process, and the material can be usedfor partially filling the holes on the substrate prior to a coveringwith the photoresist.

In addition, the composition for forming anti-reflective coatingaccording to the present invention can control the rate of crosslinkingreaction by adding a halogen atom having a relatively large atom volumein the vicinity of a hydroxy group being a crosslinkable group. In acase where an aromatic hydrocarbon instead of a halogen atom, whichmakes the rate of crosslinking reaction smaller, is added in thevicinity of a crosslinkable group, the composition for forminganti-reflective coating is difficult to afford a larger dry etching ratecompared with a resist. The composition for forming anti-reflectivecoating in which the above-mentioned halogen-containing resin is usedhas characteristics that it can appropriately repress the rate ofcrosslinking reaction and gives a high planarization, and the same timeit affords a larger dry etching rate compared with a resist as it canmake a concentration of carbon atoms therein low.

The composition for forming anti-reflective coating according to thepresent invention has no diffusion material in the resist when it isheated and dried, because the light absorbing moiety is linked to theside chain of the polymer. In addition, the composition has a highanti-reflective effect as the light absorbing moiety has fully largeabsorptivity coefficient, and further the composition does not lead to alowering of dry etching rate even when an amount of added lightabsorbing moiety is increased in order to improve absorbance, as carbonforming a ring, such as an aromatic ring in the light absorbing moietyis low in the content ratio (weight ratio).

The composition for forming anti-reflective coating according to thepresent invention can be used, depending on process condition, as acoating having a function for preventing a light reflection and afunction for preventing an interaction between a substrate and a resistor preventing an adverse effect on the substrate by materialsconstituting the resist or materials generated in exposure to theresist.

In the meantime, in a case where the anti-reflective coating of thepresent invention is used as a coating excellent in planarization ratherthan applicability, the light absorptive polymer therein is lowered inglass transition temperature (Tg) and thereby causing a little fluidityon baking and making a completely solidified coating insoluble in asolvent for the resist. For this purpose, crosslinking function of thelight absorptive polymer due to heat may be lowered a little. In orderto achieve such a planarization, degree of polymerization of the lightabsorptive polymer, concentration of the light absorptive polymer in thecomposition, the kind of the repeated unit and the substituents therein,and the kind of comonomers, and the kind of added components areappropriately selected.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing a state where a composition forforming anti-reflective coating is applied on a substrate having holes,wherein a is a recess depth (μm) of the anti-reflective coating at thecenter of the hole, and b is a depth (μm) of the hole in the substrateon which the anti-reflective coating has not been applied.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described based on examples.

SYNTHESIS EXAMPLE 1

A halogen-containing novolak epoxy resin (trade name: BREN-304manufactured by Nippon Kayaku Co., Ltd.) was prepared. The resin had aweight average molecular weigh of 900 and a structure of formula (14).

After 100.0 g of the halogen-containing novolak epoxy resin wasdissolved in 251.3 g of propylene glycol monomethyl ether, 67.6 g of9-anthracenecarboxylic acid and 1.05 g of benzyltriethylammoniumchloride were added. These compounds were reacted at 100° C. for 24hours to obtain a polymer. The resulting polymer was subjected to GPCanalysis and had a weight average molecular weight of 1,900 in terms ofstandard polystyrene. The structure of the resulting resin was shown byformula (15).

In formula (15), the molar ratio of n8: n5 in the whole polymer was5:95, and n6 was 1.7.

SYNTHESIS EXAMPLE 2

After 26 g of glycidyl methacrylate monomer and 57 g ofhydroxypropylmethacrylate were dissolved in 331 g of propylene glycolmonomethyl ether to obtain a reaction solution, nitrogen was flowed intothe reaction solution for 30 minutes. While the reaction solution wasmaintained at 70° C., 0.8 g of azobisisobutyronitrile (AIBN) as apolymerization initiator and 0.3 g of 1-dodecanethiol as a chaintransfer agent were added therein and stirred under nitrogen atmosphere.After stirring for 24 hours, 0.1 g of 4-methoxyphenol as a short-stopwas added therein. The resulting polymer was subjected to GPC analysisand had a weight average molecular weight of 36,400 in terms of standardpolystyrene. The solid content in the solution was 20%.

The resulting resin was a copolymer of glycidyl methacrylate withhydroxypropylmethacrylate corresponding to a structure of formula (16),wherein the molar ratio of m: n was 35:65.

To 64 g of the reaction solution containing 6.4 g of the resin obtainedabove, 6.8 g of 9-anthracenecarboxylic acid and 0.19 g ofbenzyltriethylammonium chloride were added, and then these compoundswere reacted at 105° C. for 24 hours to obtain a polymer. The resultingpolymer was subjected to GPC analysis and had a weight average molecularweight of 53,000 in terms of standard polystyrene. The structure of theresulting resin was shown by formula (17).

SYNTHESIS EXAMPLE 3

As a reaction solution, 300 g of a polymer solution (manufactured byLancaster Co., Ltd.) in which p-hydroxystyrene monomer was dissolved in20% by weight of solid concentration in propylene glycol was prepared.Nitrogen was flowed into the reaction solution for 30 minutes. While thereaction solution was maintained at 70° C., 0.1 g ofazobisisobutyronitrile (AIBN) as a polymerization initiator was addedtherein and stirred under nitrogen atmosphere. The reactant wasprecipitated again in 1 liter of distilled water and the precipitate wasfiltered and dried to obtain a polymer in a shape of powder. Theresulting polymer was subjected to GPC analysis and had a weight averagemolecular weight of 21,000 in terms of standard polystyrene. Theresulting polymer was poly p-vinylphenol corresponding to a structure offormula (18).

SYNTHESIS EXAMPLE 4

A brominated bisphenol A epoxy resin (trade name: YDB400 manufactured byTouto Chemical Co., Ltd.) was prepared. The resin had a weight averagemolecular weigh of 1,200 and a structure of formula (19).

After 60.0 g of the brominated bisphenol A epoxy resin was dissolved in137.0 g of propylene glycol monomethyl ether, 31.5 g of9-anthracenecarboxylic acid and 1.1 g of benzyltriethylammonium chloridewere added. These compounds were reacted at 100° C. for 24 hours toobtain a polymer. The resulting polymer was subjected to GPC analysisand had a weight average molecular weight of 1,700 in terms of standardpolystyrene. The structure of the resulting resin was shown by formula(20).

EXAMPLE 1

35.0 g of a solution containing 13.6 g of the novolak resin obtained inSynthesis Example 1 was mixed with 33.9 g of a solution containing 6.8 gof the acrylic resin obtained in Synthesis Example 2, 4.5 g ofhexamethoxymethylmelamine as a crosslinking agent, 0.138 g of pyridiniump-toluenesulfonate as a curing agent and 0.30 g of R-30 (manufactured byDainippon Ink and Chemicals, Inc.) as a surfactant, and dissolved in292.2 g of ethyl lactate, 137.6 g of propylene glycol monomethyl etherand 53.1 g of cyclohexanone as solvents to obtain a 4.5% solution. Then,the solution was filtered through a micro filter made of polyethylenehaving a pore diameter of 0.10 μm, and then, the solution was filteredthrough a micro filter made of polyethylene having a pore diameter of0.05 μm, to prepare an anti-reflective coating composition. The solutionwas coated on a silicon wafer using a spinner and the wafer was heatedat 205° C. for 1 minute on a hot plate to form an anti-reflectivecoating (film thickness: 0.080 μm).

The polymers in the resulting anti-reflective coating were consisted of66.7% by weight of novolak resin having a weight average molecularweight of 5,000 or less and 33.3% by weight of acrylic resin having aweight average molecular weight of 20,000 or more. Measurement of theanti-reflective coating by a spectral ellipsometer indicated arefractive index n of 1.61 and an absorptivity coefficient k of 0.51 at248 nm.

Example 2

35.0 g of a solution containing 13.6 g of the bisphenol A resin obtainedin Synthesis Example 4 was mixed with 33.9 g of a solution containing6.8 g of the acrylic resin obtained in Synthesis Example 2, 4.5 g ofhexamethoxymethylmelamine as a crosslinking agent, 0.138 g of pyridiniump-toluenesulfonate as a curing agent and 0.30 g of R-30 as a surfactant,and dissolved in 292.2 g of ethyl lactate, 137.6 g of propylene glycolmonomethyl ether and 53.1 g of cyclohexanone as solvents to obtain a4.5% solution. Then, the solution was filtered through a micro filtermade of polyethylene having a pore diameter of 0.10 μm, and then, thesolution was filtered through a micro filter made of polyethylene havinga pore diameter of 0.05 μm, to prepare an anti-reflective coatingcomposition. The solution was coated on a silicon wafer using a spinnerand the wafer was heated at 205° C. for 1 minute on a hot plate to forman anti-reflective coating (film thickness: 0.080 μm).

The polymers in the resulting anti-reflective coating were consisted of66.7% by weight of bisphenol A resin having a weight average molecularweight of 5,000 or less and 33.3% by weight of acrylic resin having aweight average molecular weight of 20,000 or more. Measurement of theanti-reflective coating by a spectral ellipsometer indicated arefractive index n of 1.59 and an absorptivity coefficient k of 0.49 at248 nm.

Example 3

35.0 g of a solution containing 13.6 g of the novolak resin obtained inSynthesis Example 1 was mixed with 33.3 g of a solution containing 6.7 gof the polyvinyl phenol resin obtained in Synthesis Example 3, 4.5 g ofhexamethoxymethylmelamine as a crosslinking agent, 0.138 g of pyridiniump-toluenesulfonate as a curing agent and 0.30 g of R-30 as a surfactant,and dissolved in 292.2 g of ethyl lactate, 137.6 g of propylene glycolmonomethyl ether and 53.1 g of cyclohexanone as solvents to obtain a4.5% solution. Then, the solution was filtered through a micro filtermade of polyethylene having a pore diameter of 0.10 μm, and then, thesolution was filtered through a micro filter made of polyethylene havinga pore diameter of 0.05 μm, to prepare an anti-reflective coatingcomposition. The solution was coated on a silicon wafer using a spinnerand the wafer was heated at 205° C. for 1 minute on a hot plate to forman anti-reflective coating (film thickness: 0.080 μm).

The polymers in the resulting anti-reflective coating were consisted of66.7% by weight of novolak resin having a weight average molecularweight of 5,000 or less and 33.3% by weight of polyvinyl phenol resinhaving a weight average molecular weight of 20,000 or more. Measurementof the anti-reflective coating by a spectral ellipsometer indicated arefractive index n of 1.54 and an absorptivity coefficient k of 0.35 at248 nm.

Example 4

35.0 g of a solution containing 13.6 g of the bisphenol A resin obtainedin Synthesis Example 4 was mixed with 33.3 g of a solution containing6.7 g of the polyvinyl phenol resin obtained in Synthesis Example 3, 4.5g of hexamethoxymethylmelamine as a crosslinking agent, 0.138 g ofpyridinium p-toluenesulfonate as a curing agent and 0.30 g of R-30 as asurfactant, and dissolved in 292.2 g of ethyl lactate, 137.6 g ofpropylene glycol monomethyl ether and 53.1 g of cyclohexanone assolvents to obtain a 4.5% solution. Then, the solution was filteredthrough a micro filter made of polyethylene having a pore diameter of0.10 μm, and then, the solution was filtered through a micro filter madeof polyethylene having a pore diameter of 0.05 μm, to prepare ananti-reflective coating composition. The solution was coated on asilicon wafer using a spinner and the wafer was heated at 205° C. for 1minute on a hot plate to form an anti-reflective coating (filmthickness: 0.080 μm).

The polymers in the resulting anti-reflective coating were consisted of66.7% by weight of bisphenol A resin having a weight average molecularweight of 5,000 or less and 33.3% by weight of polyvinyl phenol resinhaving a weight average molecular weight of 20,000 or more. Measurementof the anti-reflective coating by a spectral ellipsometer indicated arefractive index n of 1.51 and an absorptivity coefficient k of 0.31 at248 nm.

COMPARATIVE EXAMPLE 1

29.7 g of a solution containing 11.9 g of the resin obtained inSynthesis Example 1 was mixed with 2.76 g of hexamethoxymethylmelamineas a crosslinking agent, 0.193 g of pyridinium p-toluenesulfonate as acuring agent and 0.060 g of R-30 as a surfactant, and dissolved in 99.8g of ethyl lactate, 42.8 g of butyl lactate, 67.8 g of propylene glycolmonomethyl ether and 57.0 g of cyclohexanone as solvents to obtain a5.0% solution. Then, the solution was filtered through a micro filtermade of polyethylene having a pore diameter of 0.10 μm, and then, thesolution was filtered through a micro filter made of polyethylene havinga pore diameter of 0.05 μm, to prepare an anti-reflective coatingcomposition. The solution was coated on a silicon wafer using a spinnerand the wafer was heated at 205° C. for 1 minute on a hot plate to forman anti-reflective coating (film thickness: 0.080 μm).

The polymers in the resulting anti-reflective coating were consisted of100% of novolak resin having a weight average molecular weight of 5,000or less. Measurement of the anti-reflective coating by a spectralellipsometer indicated a refractive index n of 1.65 and an absorptivitycoefficient k of 0.53 at 248 nm.

COMPARATIVE EXAMPLE 2

10 g of a solution containing 2.0 g of the resin obtained in SynthesisExample 2 was mixed with 0.264 g of hexamethoxymethylmelamine as acrosslinking agent and 0.010 g of p-toluenesulfonic acid as a curingagent, and dissolved in 14.48 g of propylene glycol monomethyl etheracetate and 25.77 g of propylene glycol monomethyl ether as solvents toobtain a 4.5% solution. Then, the solution was filtered through a microfilter made of polyethylene having a pore diameter of 0.10 μm, and then,the solution was filtered through a micro filter made of polyethylenehaving a pore diameter of 0.05 μm, to prepare an anti-reflective coatingcomposition. The solution was coated on a silicon wafer using a spinnerand the wafer was heated at 205° C. for 1 minute on a hot plate to forman anti-reflective coating (film thickness: 0.080 μm).

The polymers in the resulting anti-reflective coating were consisted of100% of acrylic resin having a weight average molecular weight of 20,000or more. Measurement of the anti-reflective coating by a spectralellipsometer indicated a refractive index n of 1.50 and an absorptivitycoefficient k of 0.48 at 248 nm.

COMPARATIVE EXAMPLE 3

15.0 g of a solution containing 6.1 g of the novolak resin obtained inSynthesis Example 1 was mixed with 71.0 g of a solution containing 14.2g of the acrylic resin obtained in Synthesis Example 2, 4.5 g ofhexamethoxymethylmelamine as a crosslinking agent, 0.138 g of pyridiniump-toluenesulfonate as a curing agent and 0.30 g of R-30 as a surfactant,and dissolved in 292.2 g of ethyl lactate, 122.6 g of propylene glycolmonomethyl ether and 53.1 g of cyclohexanone as solvents to obtain a4.5% solution. Then, the solution was filtered through a micro filtermade of polyethylene having a pore diameter of 0.10 μm, and then, thesolution was filtered through a micro filter made of polyethylene havinga pore diameter of 0.05 μm, to prepare an anti-reflective coatingcomposition. The solution was coated on a silicon wafer using a spinnerand the wafer was heated at 205° C. for 1 minute on a hot plate to forman anti-reflective coating (film thickness: 0.080 μm).

The polymers in the resulting anti-reflective coating were consisted of30% by weight of novolak resin having a weight average molecular weightof 5,000 or less and 70% by weight of acrylic resin having a weightaverage molecular weight of 20,000 or more. Measurement of theanti-reflective coating by a spectral ellipsometer indicated arefractive index n of 1.61 and an absorptivity coefficient k of 0.51 at248 nm.

COMPARATIVE EXAMPLE 4

45.0 g of a solution containing 18.0 g of the novolak resin obtained inSynthesis Example 1 was mixed with 14.7 g of a solution containing 2.93g of the acrylic resin obtained in Synthesis Example 2, 4.5 g ofhexamethoxymethylmelamine as a crosslinking agent, 0.138 g of pyridiniump-toluenesulfonate as a curing agent and 0.30 g of R-30 as a surfactant,and dissolved in 292.2 g of ethyl lactate, 146.6 g of propylene glycolmonomethyl ether and 53.1 g of cyclohexanone as solvents to obtain a4.5% solution. Then, the solution was filtered through a micro filtermade of polyethylene having a pore diameter of 0.10 μm, and then, thesolution was filtered through a micro filter made of polyethylene havinga pore diameter of 0.05 μm, to prepare an anti-reflective coatingcomposition. The solution was coated on a silicon wafer using a spinnerand the wafer was heated at 205° C. for 1 minute on a hot plate to forman anti-reflective coating (film thickness: 0.080 μm).

The polymers in the resulting anti-reflective coating were consisted of86.0% by weight of novolak resin having a weight average molecularweight of 5,000 or less and 14.0% by weight of acrylic resin having aweight average molecular weight of 20,000 or more. Measurement of theanti-reflective coating by a spectral ellipsometer indicated arefractive index n of 1.61 and an absorptivity coefficient k of 0.51 at248 nm.

The solutions obtained in Examples 1 to 4 and Comparative Examples 1 to4 were coated on silicon wafers by means of a spinner. The coatedsilicon wafers were heated at 205° C. for 1 minute on a hot plate toform anti-reflective coatings (film thickness: 0.080 μm). Theanti-reflective coatings were dipped in a solvent used for resists, forexample, ethyl lactate and propylene glycol monomethyl ether and as aresult it was confirmed that these coatings were insoluble in thesesolvents.

The solutions obtained in Examples 1 to 4 and Comparative Examples 1 to4 were coated on silicon wafers by means of a spinner. The coatedsilicon wafers were heated at 205° C. for 1 minute on a hot plate toform anti-reflective coatings (film thickness 0.080 μm) and filmthickness was measured. On each anti-reflective coating for lithographywas coated a commercially available resist solution (trade name: APEX-Eor the like manufactured by Shipley Co., Ltd.) by means of a spinner.The coated wafers were heated at 90° C. for 1 minute on a hot plate.After exposure of the resists to light, post exposure bake was performedat 90° C. for 1.5 minutes. After developing the resists, the filmthickness of the anti-reflective coatings was measured and as a resultit was confirmed that no intermixing occurred between theanti-reflective coatings for lithography obtained in Examples 1 to 4 andComparative Examples 1 to 4 and the resist layers.

The solutions of compositions for forming anti-reflective coatingobtained above were coated on silicon wafers having holes (diameter:0.20 μm, depth: 1.0 μm) by means of a spinner. The coated silicon waferswere heated at 205° C. for 1 minute on a hot plate to formanti-reflective coatings (film thickness: c.a. 0.080 μm). Theapplicability of the anti-reflective coatings to substrates having holeswas evaluated by observing sectional shape of silicon wafer substrateshaving holes on which the anti-reflective coatings were applied.

The applicability to substrates having holes was evaluated on thefollowing items.

Test No. (1) is a test in which filling rate (% by volume) of ananti-reflective coating into holes is determined. The criteria forevaluation are as follows: a case where the filling rate falls in 30 to70% is indicated by the mark “⊚”; a case where the filling rate falls in20 to 30% or 70-80% is indicated by the mark “◯”; and a case where thefilling rate falls in a range other than the above (that is 0-20% or80-100%) is indicated by the mark “x”.

Test No. (2) confirms whether or not there are voids or gaps of air inholes. The criteria for evaluation are as follows: a case where there isno voids or gaps is indicated by the mark “⊚”; and a case where thereare voids or gaps is indicated by the mark “x”.

Test No. (3) is a measurement of thickness of anti-reflective coatingadhered to side walls of holes. The criteria for evaluation are asfollows: a case where the thickness is 20 nm or less is indicated by themark “⊚”; a case where the thickness is 20 to 40 nm is indicated by themark “◯”; and a case where the thickness is 40 nm or more is indicatedby the mark “x”.

Test No. (4) is a measurement of thickness of anti-reflective coating atupper parts of hole edges. The criteria for evaluation are as follows: acase where the thickness is 40 nm or more is indicated by the mark “⊚”;a case where the thickness is 20 to 40 nm is indicated by the mark “◯”;and a case where the thickness is 20 nm or less is indicated by the mark“x”.

Test No. (5) is a measurement of difference of coating-thickness betweenDENSE and ISO parts of holes on substrate. The criteria for evaluationare as follows: a case where the difference is 40 nm or less isindicated by the mark “⊚”; a case where the difference is 40 to 60 nm isindicated by the mark “◯”; and a case where the difference is 60 nm ormore is indicated by the mark “x”.

The filling rate was calculated according to the following equation. Thefilling rate was 100% when the holes on the substrate were completelyplanarized.

Filling Rate=[1−(recess depth (a) of anti-reflective coating at thecenter of hole)/(depth (b) of hole)]×100

The substrate subjected to the test is a silicon wafer substrate havingIso and Dense patterns of holes as shown in FIG. 1. The Iso pattern is apattern in which the distance between the center of a hole and thecenter of the adjacent hole is three times the diameter of the holes.The Dense pattern is a pattern in which the distance between the centerof a hole and the center of the adjacent hole equals to the diameter ofthe holes. The depth of hole is 1.0 μm and the diameter of hole is 0.20μm. TABLE 1 Test No. 1 2 3 4 5 Example 1 ⊚ ⊚ ⊚ ⊚ ⊚ Example 2 ⊚ ⊚ ⊚ ⊚ ◯Example 3 ⊚ ⊚ ⊚ ◯ ◯ Example 4 ⊚ ⊚ ⊚ ◯ ◯ Comparative X ⊚ ⊚ X X Example 1Comparative ◯ X X ⊚ ⊚ Example 2 Comparative ◯ X ◯ ◯ ⊚ Example 3Comparative X ⊚ ◯ X ◯ Example 4

As to Test No. (1), the filling rate (% by volume) was 80 to 100% inComparative Examples 1 and 4, and the filling rate (% by volume) was 20to 30% in Comparative Examples 2 and 3.

It became clear that Examples 1 to 4 fulfill required characteristicscompared with Comparative Examples 1 to 4. This is due to that the basepolymer in compositions for forming anti-reflective coating in Examples1 to 4 is a mixture of polymers comprising a polymer with a molecularweight of 5,000 or less and a polymer with a molecular weight of 20,000or more in a specific ratio.

The present invention relates to compositions for forminganti-reflective coatings by which control of applicability on substrateshaving holes is aimed. The resulting anti-reflective coatings areeffective in not only anti-reflection of the substrates but alsoprotection of material of hole bottom in etching process or ashingprocess.

The present invention provides compositions for forming anti-reflectivecoating which is excellent in step coverage on a substrate with anirregular surface, such as hole or trench, has a higher dry etching ratecompared with the resist layer and a high anti-reflection, and furthercauses no intermixing with a resist layer nor diffusion into the resistduring drying under heating, and has a high resolution and an excellentfilm thickness-dependence; and a method for forming an excellent resistpattern. Further, the present invention provides also excellent methodsfor forming resist patterns.

1. A composition for forming anti-reflective coating for use in alithography process in manufacture of a semiconductor device, comprisinga polymer (A) having a weight average molecular weight of 5,000 or less,and a polymer (B) having a weight average molecular weight of 20,000 ormore.
 2. The composition for forming anti-reflective coating accordingto claim 1, wherein the polymer (A) is a halogenated bisphenol A resinhaving a weight average molecular weight of 700 to 5,000.
 3. Thecomposition for forming anti-reflective coating according to claim 2,wherein the halogenated bisphenol A resin comprises at least a polymerof formula (1):

wherein X¹ is a halogen atom, n1 is the number of repeated units and aninteger of 1 to 50, n2 and n3 is the number of substituent X¹ on abenzene ring and an integer of 1 to 3, and Y is a group of formula (2)

wherein T¹ is a divalent linking group, P is a (n4+1) valent aromaticring group having 6 to 14 carbon atoms, M is an electron-donating group,n4 is the number of substituent M on P and an integer of 0 to 3, in acase where n4 is 2 or 3, substituents M are the same or different fromeach other.
 4. The composition for forming anti-reflective coatingaccording to claim 1, wherein the polymer (A) is a halogen-containingnovolak resin having a weight average molecular weight of 600 to 5,000.5. The composition for forming anti-reflective coating according toclaim 4, wherein the halogen-containing novolak resin is a polymerhaving at least a repeated unit of formula (3):

wherein T² is a divalent linking group, X² is chlorine atom or bromineatom, n5 is the number of repeated units, n6 is the number ofsubstituent X² on a benzene ring and an integer of 1 to 3, P is a (n7+1)valent aromatic ring group having 6 to 14 carbon atoms, M is anelectron-donating group, n7 is an integer of 0 to 3, in a case where n7is 2 or 3, substituents M are the same or different from each other. 6.The composition for forming anti-reflective coating according to claim1, wherein the polymer (B) is a polyacrylate or polymethacrylate havinga weight average molecular weight of 20,000 to 200,000.
 7. Thecomposition for forming anti-reflective coating according to claim 1,wherein the polymer (B) is a polystyrene or a derivative thereof hawinga weight average molecular weight of 20,000 to 200,000.
 8. Thecomposition for forming anti-reflective coating according to claim 1,containing the polymer (A) in an amount of 33.7 to 83.2% by weight andthe polymer (B) in an amount of 66.3 to 16.8% by weight.
 9. Thecomposition for forming anti-reflective coating according to claim 1,further containing a crosslinking agent having at least twocrosslink-forming functional groups.
 10. The composition for forminganti-reflective coating according to claim 1, wherein the composition isused for a production of a semiconductor device by a method comprisingcovering a substrate having holes of an aspect ratio indicated byheight/diameter of 1 or more with a photoresist, and transferring animage on the substrate by utilizing a lithography process, and thecomposition is used for partially filling the holes on the substrateprior to a covering with the photoresist.
 11. The composition forforming anti-reflective coating according to claim 10, wherein thefilling of the holes is carried out in a rate of 20 to 80% based on avolume per hole.
 12. A process for manufacturing a semiconductor deviceby transferring an image on a substrate and forming an integratedcircuit element, comprising the steps (I), (II) and (III) of: Step (I):a step comprising coating the composition for forming anti-reflectivecoating according to claim 1 on a substrate having holes of an aspectratio indicated by height/diameter of 1 or more, and drying thecomposition to fill 20 to 80% of a volume of holes on the substrate withthe anti-reflective coating; Step (II): a step comprising coating aresist and drying it; and Step (III): a step comprising exposing tolight, developing and etching.